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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 1 An ATSC Detector using Peak Combining IEEE P802.22 Wireless RANs Date: 2006-11-13 Authors: Notice: This document has been prepared to assist IEEE 802.22. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEEs name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEEs sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.22. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures http://standards.ieee.org/guides/bylaws/sb-bylaws.pdf including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chairhttp://standards.ieee.org/guides/bylaws/sb-bylaws.pdf Carl R. StevensonCarl R. Stevenson as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.22 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at patcom@iee.org.patcom@iee.org >

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 2 Abstract This presentation introduces an ATSC detector based on combining peaks from the output of a correlator for the ATSC Data Field Sync pattern A special case of this approach is taking the maximum of the correlator output. This will be evaluated first before considering the more general case Probability of misdetection curves are given for the 12 preferred ATSC signal files The results of these curves are averaged to get an average probability of misdetection curve Finally, the results are averaged over the shadow fading probability density function

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 3 Background In [1] we evaluated a technique in the 802.22 working document for ATSC signal detection We suggested a simpler method which actually gave better performance In [1] we only evaluated these methods using one ATSC signal file In this presentation we evaluate the simple method using the 12 preferred signal files

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 4 ATSC Frame Structure A single VSB Data Segment The Data Field SYNC

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 5 Background Convert the receive signal to baseband and then correlate the received baseband signal with the ATSC Field Sync pattern The correlator output is observed for one ATSC Data Field (24.2 ms) Use the simple test statistic,

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 6 Peak Combining We will like to be able to combine the peaks from multiple ATSC Data Fields A simple approach is to effectively increase the correlator to cover multiple ATSC Data Fields However, there are two issues with approach –Due to clock jitter the peaks shift slightly in each Data Field –Due to multipath the polarity of the peak can reverse –Also, there are sometime a few peaks due to multipath Can we come up with a method of combining peaks from multiple ATSC Data Fields?

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 7 Peak Combining To address the issue of polarity reversal we start by taking the absolute value of the correlator output The next step is to select N possible candidate peaks from each ATSC Data Field. These are the N largest peaks. We generate a table of peaks from each ATSC Data Field. A peak is represented by, –A peak index (the sample index starting from the beginning of that ATSC data field) –A peak magnitude

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 8 Peak Combining – Correlator Output

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 9 Peak Combining – Absolute Value of Correlator Output

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 10 Peak Combining – Peak List Peak IndexPeak Magnitude i1i1 p1p1 i2i2 p2p2 i3i3 p3p3 i4i4 p4p4 i5i5 p5p5 i6i6 p6p6

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 11 Peak Combining – Overlay Peaks from Multiple ATSC Data Fields

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 12 Combine peaks whose index fall with within a window of size M

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 13 Final Test Statistic Select the maximum magnitude of the final peak list as the test statistic For the case when we only process for one ATSC Data Field this is the same as the maximum of the absolute value of the correlator output

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 14 Observations The actual peaks (the ones due to a correlation with the ATSC Data Field) tend to combine since they are within the window size The false peaks (those due to noise) tend to not combine very often since they tend to occur at different times within the field We do need to increase the detector threshold a bit since observing over a longer time and peak combining does result in a small increase in the test statistic due to noise only

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 15 Average Probability of Misdetection Simulated the peak combining technique for all twelve of the preferred ATSC signal files Simulations for two detectors –One ATSC Data Field (already shown earlier) –Four ATSC Data Fields Show the results for all twelve signal files Averaged the results for all twelve signal files to obtain the average probability of misdetection

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 16 Probability of Misdetection Curves

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 17 Probability of Misdetection Curves

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 18 P MD Averaged over all 12 ATSC Data Files

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 19 Average over Shadow Fading We can now average over the PDF of the shadow fading to obtain the average probability of misdetection at the edge of the keep-out region Mean signal power = -96.5 dBm [2] Standard deviation of the signal power = 5.5 dB [2] Noise Power = -95.2 dBm [2] Combining we get Average SNR = 1.3 dB Standard deviation of SNR = 5.5 dB

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 20 Shadow Fading PDF

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 21 Average P MD We can average the P MD functions on Slide 18 by numerically integrating over the shadow fading PDF Number of ATSC Data Fields P MD 10.05 40.028

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 22 Conclusions A new technique for detection of ATSC signals was proposed utilizing the unique ATSC Data Field Sync pattern The results give reasonable results but do not yet reach the sensing requirements for ATSC Averaging over the ATSC signal files and the shadow fading gives the average probability of misdetection at the edge of the keep-out region, which is a excellent summary of a detectors performance The time required for detection using the ATSC Data Sync is in the tens or hundreds of ms since the pattern occurs every 24.2 ms

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doc.: IEEE 802.22-06/243r0 Submission November 2006 Steve Shellhammer, QualcommSlide 23 References 1.Suhas Mathur and Steve Shellhammer, An Evaluation of the PN Sequence based detection of DTV Signals in the Draft, IEEE 802.22-06/0189r0, September 2006 2.Steve Shellhammer, Victor Tawil, Gerald Chouinard, Max Muterspaugh and Monisha Ghosh, Spectrum Sensing Simulation Model, IEEE 802.22-06/0028r10, August 2006

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